The invention relates to the field of microphones, and in particular to microphones with mute and keep alive functions.
Speech recognition software is a tool for increasing office productivity, particularly for entering text in word processing applications with personal computers. Such software performs best when the voice input is provided via a xe2x80x9cclose talkingxe2x80x9d headset microphone, that is a microphone with acoustic cancellation of background noise. Desk or monitor supported microphones may also be used successfully in quiet environments. The microphone signal is applied to the corresponding input connector of the computer sound card. It is evident that by wearing a headset, dictation becomes a hands-free operation and is therefore valuable for individuals with limited use of hands or arms. When the person dictating text into the microphone wishes instead to speak with a person in the area, an awkward situation develops in which the operator has to remember and say xe2x80x9cgo to sleepxe2x80x9d or xe2x80x9cstop listeningxe2x80x9d to the speech recognition software. This will prevent the computer from recording the person to person conversation, however, resumption of proper dictation will require another spoken command such as xe2x80x9cwake upxe2x80x9d or xe2x80x9clisten to me.xe2x80x9d
It is therefore appropriate to interpose a mute switch between the microphone and the computer sound card. An exemplary headset product is the VXI Corporation model Parrott QD-10 with a QD 500 mute switch. Such switches are also used with telephony headsets where the mute function prevents the calling party (perhaps the customer) from hearing the called party (a service agent) while he or she asks another agent a question. An exemplary telephony headset is VXI Corporation model PB-QD-10-6, again with a QD 500 mute switch. Microphone mute switches are configured for xe2x80x9cclicklessxe2x80x9d operation where electrical transients are suppressed and hence objectionable audible clicks are prevented. The resulting silence while muted to the computer creates an undesirable condition for the software: the speech recognition program hears nothing, attempts to increase microphone sensitivity to process inaudible information and becomes saturated (causing a significant delay of several seconds) when the mic is unmuted and voice returns to the computer.
Accordingly, the invention provides in an exemplary embodiment a microphone system including a microphone for inputting voice data, an output for transmitting the voice data to a device connectable thereto; and a circuit which operates to mute the voice data and provide a signal to the device in order to maintain a suspended state of operation in the device. In accordance with one aspect of the invention, the device is a computer that is responsive to voice data, for example, by utilizing voice recognition software.
The invention provides a microphone with mute switch and circuitry. When the microphone is muted, a xe2x80x9ckeep alivexe2x80x9d circuit will inject a signal into the computer microphone input. This signal has characteristics unlike speech, thus preventing misinterpretation and is of sufficient amplitude to inhibit attempts by the software to increase microphone sensitivity. The circuit is powered from the current limited mic bias source provided by the sound card, thus requiring no external batteries. A mic bias current is required by the electret, which is the microphone type most frequently used in telephony and voice-enabled computer applications. However, the invention applies equally when the less common dynamic microphones are used instead. Additional circuitry is provided for optimum utilization of the limited DC power available from the sound card when either the microphone or the xe2x80x9ckeep alivexe2x80x9d stage is energized. Personal computer xe2x80x9csound cardxe2x80x9d circuits are now commonly part of the system board (motherboard), but appear no different at the mic input connector.
Related techniques for xe2x80x9ckeep alivexe2x80x9d functions are described in co-pending U.S. patent application Ser. No. 09/130,745 filed Aug. 7, 1998 and for optimum. DC power extraction in Ser. No. 09/115,980 filed Jul. 15, 1998, both of common assignee.